JPS5978999A - Manufacture of semiconductor single crystal film - Google Patents

Abstract

PURPOSE:To enlarge the grain of a single crystal, by irradiating a semiconductor films doubly with laser light and light having the larger absorptivity than the laser light when a polycrystalline or amorphous semiconductor film on a substrate is to be converted to a single crystal. CONSTITUTION:Polycrystalline or amorphous silicon film 2 is piled up on the surface of a substrate 1 such as glass or the like and the lamp light B shaped by a slit and the CWNd:YAG laser beam 4 shaped to a semicircular form by a slit are irradiated doubly on the film. Said irradiation is carried out under the condition so that the silicon film 2 is melted and scanned in the direction showen by the arrow 5. The melted silicon layer 6 is solidified and a silicon single crystal 7 having a large grain size is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor single crystal film, and particularly to a method for single crystallizing a polycrystalline or amorphous conductor film formed on a substrate.

Single crystallization of polycrystalline or amorphous semiconductor films by laser beam irradiation generally uses an argon (hereinafter abbreviated as Ar) laser or a neodymium YAG (hereinafter abbreviated as N (1: YAG) laser). This is done using a single laser beam.

Taking a silicon film as an example, since an Ar laser has a larger absorption coefficient than a silicon film, it is easy to melt the silicon film. However, for example, when converting a polycrystalline silicon film on an insulator into a single crystal, the film thickness varies from 0.3 to
The applicable range is about 0.8 μm, and if it is thick, the entire layer cannot be melted, and if it is thin, the film is likely to scatter. On the other hand, when a Nd:YAG laser (wavelength: 1.06 μm) is used, the absorption coefficient for silicon is small, so a film with a thickness of 0.5 μm or more has the disadvantage of being easily scattered. As shown in the example above, when recrystallization is performed using only a single CW laser beam, the temperature distribution in the film thickness direction is determined by the absorption coefficient of the wavelength of the laser beam into the semiconductor film. There was a problem in that the more the film deviated from the film thickness, the more difficult it was to perform proper one-step melting.

Ab-Ride Physics Letters (App l 1ed) as a single crystallization method for polycrystalline silicon films on insulating substrates.
Physics Letters) Volume 37 (1
980) on pages 454-456 of the paper ``Silicon graphoepitaxy using a stripe heater open''.
itaxy using a 5tripe -
Heater oven) In J, by melting silicon with a carbon heater and scanning the carbon heater, the temperature was 10 times higher than when using a laser.
It was shown that grains that were more than twice as large grew (・).

This is thought to be due to the fact that when a heater is used, the temperature change during recrystallization is gradual, but when a laser is used, the temperature drops rapidly after the beam passes, causing the grain size to increase. It had the disadvantage of being limited.

The present invention is intended to improve the drawbacks observed in conventional single laser beam irradiation, and is directed to applying a laser beam to a polycrystalline or amorphous semiconductor film formed on a substrate, and applying the laser beam to the semiconductor film. The method is characterized in that the semiconductor film is made into a single crystal by irradiating the semiconductor film with light having a large absorption coefficient in a superimposed manner.

If the method of the present invention is used, for example, N
Even when the absorption coefficient is small, such as d:YAG, the power of Na:YAG can be effectively utilized by increasing the absorption coefficient, and therefore the semiconductor film can be melted and made into a single crystal with lower power than before. As a direct effect, the diameter of the laser beam can be expanded, which has the advantage of increasing the size of the grain and shortening the time required to anneal the entire surface. In addition, since it is possible to melt the area where the light and laser beam overlap, by shaping the irradiation area with slits etc., it is possible to easily control the temperature distribution in the plane, that is, the cooling direction, and the grain It has the advantage that it can be made even larger.

The details of the invention will be explained with reference to the drawings showing examples.

FIGS. 1(a) and 1(b) are a sectional view and a plan view of an irradiation area of an embodiment of the present invention. The structure of the substrate is not limited to that shown in FIG. 1(a). A polycrystalline or amorphous silicon film 2 is deposited on a glass substrate 1, lamp light 3 is shaped by a slit, and CW Nd is formed into a half-moon shape by the slit.
The YAG laser 4 is irradiated in layers. When irradiation is performed under conditions that melt the silicon film 2 and scanned in the direction of arrow 5,
The molten silicon layer 6 solidifies into silicon crystals 7 with large grains.

When the lamp light 3 and the CWNd:YAG laser 4 are overlapped as shown in FIG. Not only does laser absorption increase, but C
Even in the region not irradiated with the WNd:YAG laser, carriers exist due to absorption of light, so the thermal conductivity increases and the molten silicon 6 grows more slowly, excluding gate crystallization, and the grains become larger. Therefore, a region in which the orientation is controlled (typically, an insulating film is formed on a crystalline silicon substrate, a part of it is etched away, and a polycrystalline silicon film is formed on the entire surface) By growing from the tactile part of the membrane, it is possible to widen the area where single crystals form, 40μm x 200μ? A large grain size on the order of n was obtained.

Another example of how lamp light and laser light are superimposed is shown in FIG. 8 is a laser beam irradiation area, and 9 is a lamp light irradiation area. When polycrystalline or amorphous semiconductor films are irradiated in a stacked state and, for example, the semiconductor film is scanned in the direction of arrow 10, recrystallization progresses in the direction of arrow 11, and the center of the laser beam passes over the semiconductor film. Because the line part becomes the core, we were able to obtain large grains.

As described above, the present invention improves the film thickness by irradiating a polycrystalline or amorphous semiconductor film with laser light and light whose absorption coefficient for the semiconductor film is larger than that of the laser light. We can provide annealing methods that can be adapted to different types of materials and structures. In addition, the absorption coefficient of /J% for the semiconductor film is
- Compared to annealing with laser light alone, the power of laser light can be used more effectively by irradiating the light in layers,
As a result, the irradiation area of the laser can be expanded since a lower power density is sufficient, resulting in significant effects in shortening the annealing time per unit area and increasing the grain size.

Furthermore, since the laser beam and the light for increasing the absorption coefficient are not strong enough to melt the semiconductor film by themselves, shaping with a slit or the like is easier than in the past.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, in which (a) is a cross-sectional view and (b) is a plan view of the irradiation area. Also, the second time,
1 is a glass substrate; 2 is a polycrystalline or amorphous silicon film; 3 is a laser beam; 4 is a lamp beam; Molten silicon, 7 is 1J crystallized silicon film, +! ! ?
I? -8 is the laser beam irradiation area l. , 9 indicates the irradiation area of the lamp light, 10 indicates the scanning direction of trial scanning, and 11 indicates the six crystallization directions, respectively. 527--, Yuman Z figure

Claims (1)

[Claims] A polycrystalline or amorphous semiconductor film formed on a substrate is irradiated with laser light, and the semiconductor film is irradiated with light having a larger absorption coefficient than the laser light. A method for producing a semiconductor single crystal film, characterized by increasing the crystallization of the semiconductor film.